1. Field of the Invention
The present invention relates to a method of manufacturing semiconductor devices, and more particularly, to a method of forming a selective metal layer and methods of forming a capacitor of a semiconductor device and filling a contact hole using the same.
2. Description of the Related Art
As semiconductor devices become highly integrated and complicated, a metal layer must often be selectively formed while manufacturing the semiconductor devices. In a process for manufacturing a capacitor of a semiconductor device, a lower electrode is formed using a metal instead of polysilicon to obtain high capacitance, thereby achieving a metal insulator silicon (MIS) or metal insulator metal (MIM) structure. Or, in a process for filling a contact hole, an ohmic layer is formed on the bottom of a small contact hole having a high aspect ratio. The above two processes have many difficulties.
In the manufacturing process of the capacitor having the metallic lower electrode, it is very difficult to selectively deposit a metal layer without patterning the metal layer on a hemispherical grain (HSG) polysilicon lower electrode. At present, such technology is not known at all. Also, in order to use PZT(Pb(Zr,Ti)O3) or BST((Ba,Sr)TiO3), having a Perovskite structure, as a high dielectric film of a capacitor, it is preferable that platinium (Pt), which is not oxidized and has excellent leakage current properties, is used instead of an existing polysilicon electrode, when a dielectric film is deposited. However, when a metal layer such as a platinum film is deposited by a blanket method rather than a selective method, etching is hard. That is, when the platinum film formed by the blanket method is dry-etched using chlorine (Cl2) gas as an etchant, PtClx generated as a by-product of etching is a non-volatile conductive polymer. Thus, a process for removing the PtClx by wet etching must also be performed. In the wet etching process, to remove PtClx, part of a platinum lower electrode is also etched. It is therefore difficult to perform a repeatable process in a manufacturing process of a dynamic random access memory (DRAM) which requires fine patterning.
Also, the ohmic layer is formed on the bottom of the contact hole by depositing a highly conductive metal having a high melting point, such as titanium, by plasma enhanced chemical vapor deposition (PECVD) or sputtering. However, when sputtering is used to form the ohmic layer, step coverage is low. The PECVD is not suitable to apply to an actual process, since leakage current is increased by a high deposition temperature of 600xc2x0 C. or more and thus the electrical characteristics of the semiconductor devices are deteriorated.
In addition, if the ohmic layer such as a titanium (Ti) layer is formed by sputtering, and a barrier layer, e.g., a titanium nitride (TiN) layer, is formed on the ohmic layer by chemical vapor deposition (CVD), the ohmic layer may be corroded and the interface between the ohmic layer and the barrier layer may lift. If the barrier layer (TiN) is formed on a titanium (Ti) ohmic layer by sputtering, the interface between the ohmic layer and the barrier layer does not lift. However, when a plug layer for filling the contact is formed using tungsten by CVD in a subsequent process, the lifting problem occurs.
Therefore, a method is required of selectively forming a metal layer at a temperature of 500xc2x0 C. or lower where the electrical characteristics of semiconductor devices are not degraded. However, at present, it is very difficult to realize such a technique in the process of forming the lower electrode of the capacotor and forming the ohmic layer of the contact hole.
To solve the above problems, it is an objective of the present invention to provide a method of forming a selective metal layer, by which a sacrificial metal layer is selectively deposited at a temperature of 500xc2x0 C. or lower. The sacrificial metal layer is replaced with a deposition metal layer by reacting the sacrificial metal layer with a metal halide gas having a smaller halogen coherence than a metallic atom of the sacrificial metal layer.
It is another objective of the present invention to provide a method of forming a capacitor of a semiconductor device using the selective metal layer formation method.
It is still another objective of the present invention to provide a method of filling a contact hole using the selective metal layer formation method.
Accordingly, to achieve the first objective, in a selective metal layer formation method, a semiconductor substrate on which an insulating film and a conductive layer are formed is loaded into a chamber, and a purge gas, e.g. a mixture of hydrogen and silane, is supplied to the chamber. A sacrificial metal layer is formed on only the conductive layer by supplying to the chamber a sacrificial metal source gas which is deposited selectively on the conductive layer. The sacrificial metal source gas is preferably either dimethyl aluminum hydride (DMAH: (CH3)2AlH) or dimethyl ethylamine alane (DMEAA: (CH3)2C2H5N:AlH3). Finally, the sacrificial metal layer is replaced with a deposition metal layer by supplying to the chamber a metal halide gas having a halogen coherence smaller than the halogen coherence of metal atoms in the sacrificial metal layer.
According to a preferred embodiment of the present invention, the purge gas is continuously supplied, or first supplied in a predetermined amount to purge and periodically supplied in predetermined amounts after the sacrificial metal layer is formed and replaced with the deposition metal layer. Here, it is suitable that the supply time and amount of a purge gas to be supplied after replacement of the deposition metal layer are greater than in other steps.
It is suitable that the insulating film is an oxide film (SiO2) or a complex film including the oxide film, and that the conductive layer is formed of silicon doped with impurities, or a metal containing material.
Preferably, the metal containing material for the conductive layer is a refractory metal, a refractory metal nitride, a refractory metal carbide, a metal silicide, conductive Perovskite, a platinum-family metal, a conductive platinum-family nitride, or a mixture of two or more of the above materials. It is preferable that TiCl4 is used as the metal halide gas when the deposited metal is titanium. Also, it is preferable that a gas obtained by dissolving platinic chloride (Cl6H6Pt) or PtCl2 in water (H2O) or alcohol and vaporizing the dissolved Cl6H6Pt or PtCl2 is used as the metal halide gas when the deposited metal is platinum.
To achieve the second objective, in a method of forming a capacitor of a semiconductor device using a selective metal layer formation method, a contact hole exposing a source region of a semiconductor substrate is formed, by forming an insulating film such as an oxide film (SiO2) or a complex film including the oxide film on the semiconductor substrate and patterning the insulating film. A conductive layer is formed of polysilicon doped with impurities, or a metal containing material, filling the contact hole and covering the insulating film. A conductive layer pattern connected to the contact hole is formed by patterning or chemically mechanically polishing the conductive layer. The semiconductor substrate is introduced into a chamber, and a purge gas of hydrogen (H2) and silane (SiH4), is supplied to the chamber. A sacrificial metal layer is formed on only the conductive layer, by supplying to the chamber a sacrificial metal source gas which is deposited selectively on the conductive layer. Here, the sacrificial metal source gas is preferably either dimethyl aluminum hydride (DMAH: (CH3)2ALH) or dimethyl ethylamine alane (DMEAA: (CH3)2C2H5N:AlH3). Then, the sacrificial metal layer is replaced with a deposition metal layer by supplying to the chamber a metal halide gas having a halogen coherence smaller than the halogen coherence of metal atoms in the sacrificial metal layer. Finally, a dielectric film is formed on the deposition metal layer, and an upper electrode is formed on the dielectric film.
According to a preferred embodiment of the present invention, the step of forming a hemispherical grain on the surface of a conductive pattern can be performed after the conductive layer pattern is formed.
It is preferable that the purge gas is continuously supplied, or first supplied in a predetermined amount to purge and periodically supplied in predetermined amounts after the sacrificial metal layer is formed and after the sacrificial metal layer is replaced with the deposition metal layer. Here, it is proper that a purge gas supplied after the deposition metal layer is replaced has a longer supply time and greater amount of supply than a purge gas supplied in other steps.
Also, according to the preferred embodiment of the present invention, the step of siliciding the deposition metal layer can be further comprised after the step of forming the deposition metal layer.
To achieve the third objective, in a method of filling a contact hole using a selective metal layer formation method, an insulating film, such as an oxide film (SiO2) or a complex film including the oxide film, is formed on a semiconductor substrate. A contact hole exposing a lower film of polysilicon doped with impurities, or a metal such as TiN, is formed by patterning the insulating film. The semiconductor substrate on which the contact hole is formed is introduced into a chamber, and a purge gas, preferably a mixture of hydrogen (H2) and silane (SiH4), is supplied to the chamber. A sacrificial metal layer is formed of aluminum (Al) on only the lower film by supplying to the chamber a sacrificial metal source gas which is deposited selectively on the lower film. Here, the sacrificial metal source gas is either dimethyl aluminum hydride (DMAH: (CH3)2ALH) or dimethyl ethylamine alane (DMEAA: (CH3)2C2H5N:AlH3). Then, the sacrificial metal layer is replaced with a deposition metal layer by supplying a metal halide gas having a halogen coherence smaller than the halogen coherence of metal atoms in the sacrificial metal layer, to the chamber. Finally, a conductive layer filling the contact hole is formed.
According to the preferred embodiment of the present invention, the purge gas is continuously supplied, or first supplied in a predetermined amount to purge and periodically supplied in predetermined amounts after the sacrificial metal layer is formed and after the sacrificial metal layer is replaced with the deposition metal layer. Here, it is proper that a purge gas supplied after the deposited metal layer is replaced has a longer supply time and greater amount of supply than a purge gas supplied in other steps.
Also, it is preferable to form a barrier layer, e.g., a TiN layer, on a deposition metal layer after the step of replacing the sacrificial metal layer with the deposition metal layer.
According to the present invention, in a process for manufacturing semiconductor devices, a specific metal selectively formed at a temperature of 500xc2x0 C. or lower is applied to the process for forming a lower electrode of a capacitor, thereby forming a metallic lower electrode of a capacitor without serious process difficulty. Also, when the ohmic layer is formed on the bottom surface of the contact hole, property degradation or lifting of a thin film due to corrosion can be prevented, while simultaneously increasing step coverage.